A series of titanium-containing methylene-bridged compounds having the general formula ##STR3## in which the designation "Cp" stands for cyclopentadienyl and Y stands for methyl, chlorine, CD.sub.3 or CH.sub.2 C(CH.sub.3).sub.3 has been described by Tebbe et al. in a series of articles such as J.A.C.S., 100, 3611-3613 (1978) and 101, 5074-5075 (1979). These compounds are prepared by reaction of dicyclopentadienyl titanium dichloride with trimethylaluminum and are useful as reagents in Wittig reactions, converting the oxygen atom of a carbonyl group to a methylene group. The compounds are effective for methylenation of ketones and esters, as well as unsaturated hydrocarbons, but their use requires long reaction times and the process for their preparation involves trimethylaluminum, which is pyrophoric and requires special handling.